1. Field of the Disclosure
The present disclosure relates to electronic devices, and more particularly to methods of testing electronic devices.
2. Description of the Related Art
Burn-in and other types of electrical testing are typically performed on electronic devices, such as integrated circuits, before the electronic devices are shipped to customers. FIG. 1 includes an illustration of a cross-section of an electronic device 10, which includes a die 12 that has one or more circuits, electronic components, or any combination thereof (not illustrated). The die 12 is attached to a substrate 14 and is encapsulated by a case 16. The case 16 can include a ceramic material, an organic material, or other suitable material used for encapsulating the die 12. The electronic device 10 also includes electrical connectors 18 that allow signals to be transmitted from outside the electronic device 10 to the die 12. Although not illustrated, traces are embedded within the packaging substrate 14 to allow signals to pass from the electrical connectors 18 to the die 12. The electrical connectors 18 can include solder balls, pins, or other suitable terminals used to connect the electronic device 10 to an external power source, one or more other signal lines, or any combination thereof.
During burn-in or other testing of the electronic device 10, heat can be generated by the die 12. A temperature of the die (herein, “die temperature”) or the case (herein, “case temperature”) may be used to control the temperature of the electronic device 10 during burn-in or other testing. The die temperature can be determined by using a conventional or proprietary thermal diode or thermal resistor within the die 12. If the die temperature is to control the temperature, additional complexity may involve obtaining signals related to the thermal diode or resistor.
Alternatively, the case temperature is typically used because it is significantly simpler than measuring the die temperature. For example, a conventional or proprietary optical or thermal sensor can sense the case temperature. The case temperature can be measured at or near an exposed outer surface of the case, and can be monitored on a device-by-device basis. An external heating source may be used to adjust the case temperature to be within a specified range. For example, the case temperature may be set to 125° C.+/−0.5° C.
The case temperature is not an accurate predictor of the die temperature because different electronic devices may draw different currents. For example, the die temperature may vary by 20° or more between electronic devices even though the case temperatures for those electronic devices are maintained close to 125°. The difference in die temperature can significantly affect the time needed to properly burn-in the electronic device 10. Thus, skilled artisans are faced with a dilemma of using a more complicated testing set-up or procedure when measuring die temperature or use a relatively simpler but more inaccurate testing environment when the case temperature is used.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.